New applications of the genetic algorithm for the interpretation of high-resolution spectra

2004 ◽  
Vol 82 (6) ◽  
pp. 804-819 ◽  
Author(s):  
W Leo Meerts ◽  
Michael Schmitt ◽  
Gerrit C Groenenboom

Rotationally resolved electronic spectroscopy yields a wealth of information on molecular structures in different electronic states. Unfortunately, for large molecules the spectra get rapidly very congested owing to close-lying vibronic bands, other isotopomers with similar zero-point energy shifts, or large-amplitude internal motions. A straightforward assignment of single rovibronic lines and, therefore, line position assigned fits are impossible. An alternative approach is unassigned fits of the spectra using genetic algorithms (GAs) with special cost functions for evaluation of the quality of the fit. This paper decribes the improvements we established on the GA method discussed before (J.A. Hageman, R. Wehrens, R. de Gelder, W.L. Meerts, and L.M.C. Buydens. J. Chem. Phys. 113, 7955 (2000)). In particular, we succeeded in obtaining a dramatic reduction in computing time that made it possible to apply the GA process in a large number of cases. A completely automated fit of a rotationally resolved laser-induced fluorescence spectrum without any prior knowledge of the molecular parameters can now be performed in less than 1 h. We demonstrate the power of the method on a number of typical examples such as very dense rovibronic spectra of van der Waals clusters and overlapping spectra due to different isotopomers. The discussed results demonstrate the extreme power of the GA in automated fitting and assigning of complex spectra. It opens the road to the analysis of complex spectra of biomolecules and their building blocks. Key words: high-resolution spectroscopy, genetic algorithm, biomolecules, structure, van der Waals clusters.

1995 ◽  
Vol 408 ◽  
Author(s):  
M. Meierovich ◽  
A. Mushinski ◽  
M. P. Nightingale

AbstractIn a previous paper [1], we developed a form of variational trial wave function and applied it to van der Waals clusters: five or less atoms of Ar and Ne modeled by the Lennard-Jones potential. In addition, we tested the trial functions for a hypothetical, light atom resembling Ne but with only half its mass. We did not study atoms such as He4 with larger de Boer parameters, i.e., systems in which the zero point energy plays a more important role relative to the potential energy. This is the main purpose of the present paper. In fact, we study clusters to the very limit where the zeropoint energy destroys the ground state as a bound state. A simple picture of this un-binding transition predicts the power law with which the energy vanishes as the de Boer parameter approaches its critical value and the power of the divergence of the the size of the clusters in this limit. Our numerical results are in agreement with these predictions.


1998 ◽  
Vol 108 (5) ◽  
pp. 1836-1850 ◽  
Author(s):  
N. M. Lakin ◽  
G. Pietraperzia ◽  
M. Becucci ◽  
E. Castellucci ◽  
M. Coreno ◽  
...  

2003 ◽  
Vol 101 (10) ◽  
pp. 1511-1515
Author(s):  
FRANK MADEJA ◽  
ANDREAS HECKER ◽  
SIMON EBBINGHAUS ◽  
MARTINA HAVENITH

Science ◽  
1996 ◽  
Vol 272 (5268) ◽  
pp. 1631-1634 ◽  
Author(s):  
M. Hartmann ◽  
R. E. Miller ◽  
J. P. Toennies ◽  
A. F. Vilesov

2002 ◽  
Vol 09 (01) ◽  
pp. 99-104 ◽  
Author(s):  
R. FLESCH ◽  
W. TAPPE ◽  
E. RÜHL ◽  
A. A. PAVLYCHEV

High resolution near-edge excitation of isolated molecules and homogeneous molecular van der Waals clusters is reported. Resonant excitation near the element K-edges of isolated and clustered carbon monoxide and nitrogen gives rise to small spectral shifts that can only be detected by high spectral resolution. The experimental results indicate for the vibrationally resolved 1s → π* transitions of isolated molecules that symmetric line shapes cannot be used rather than the lifetime-broadened rotational fine structure. Clustered molecules exhibit characteristic redshifts of the order of a few meV relative to the corresponding isolated molecules. Changes in Franck–Condon factors and changes in spectral line shape are observed, as well. The experimental results are discussed in the framework of the quasiatomic approach with respect to intermolecular interactions and dynamic localization of resonant core-to-valence excitations.


1996 ◽  
Vol 104 (10) ◽  
pp. 3501-3510 ◽  
Author(s):  
Douglas G. Jahn ◽  
William S. Barney ◽  
Jerry Cabalo ◽  
Simon G. Clement ◽  
Andreas Rohrbacher ◽  
...  

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